JPH06-247117A, published by the Japan Patent Office in 1994, discloses the application of Sky Hook control to the damping force control of a shock absorber for a vehicle.
The control device according to this prior art calculates a damping coefficient C of the shock absorber by a relation C=Cs á V/Vs when the sign of a product of a sprung member speed V of a sprung member and a stroke speed Vs of the shock absorber is positive. In contrast, the control device calculates the damping coefficient C of the shock absorber by a relation C=Cs á V when the sign is negative. Herein. Cs denotes a Sky Hook damping coefficient.
In Sky Hook control, when the sign of the sprung member speed V and that of the stroke speed Vs of the shock absorber are identical, the Sky Hook control force is calculated by multiplying the sprung member speed V by the Sky Hook damping coefficient Cs. On the other hand, when the signs are different, control should be performed so as to cause the Sky Hook control force to become zero.
The prior art device adjusts the value of the damping coefficient C of the shock absorber such that the Sky Hook control force Cs á V, which is required when the signs of the sprung member speed V and the stroke speed Vs of the shock absorber are identical, becomes equal to a value Vs á C, which is a damping force of the shock absorber obtained as a product of the stroke speed Vs of the shock absorber and the damping coefficient C.